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close(n)		     Tcl Built-In Commands		      close(n)


       close - Close an open channel.

       close channelId

       Closes the channel given by channelId.

       ChannelId must be an identifier for an open channel such as a Tcl stan‐ │
       dard channel (stdin, stdout, or stderr), the return value from an invo‐ │
       cation  of  open or socket, or the result of a channel creation command │
       provided by a Tcl extension.

       All buffered output is flushed to  the  channel's  output  device,  any
       buffered	 input	is discarded, the underlying file or device is closed,
       and channelId becomes unavailable for use.

       If the channel is blocking, the command does not return until all  out‐ │
       put  is	flushed.  If the channel is nonblocking and there is unflushed │
       output, the channel remains open and the command	 returns  immediately; │
       output will be flushed in the background and the channel will be closed │
       when all the flushing is complete.

       If channelId is a blocking channel for a command	 pipeline  then	 close
       waits for the child processes to complete.

       If  the	channel is shared between interpreters, then close makes chan‐ │
       nelId unavailable in the invoking interpreter but has no	 other	effect │
       until  all  of  the sharing interpreters have closed the channel.  When │
       the last interpreter in which the channel is registered invokes	close, │
       the cleanup actions described above occur. See the interp command for a │
       description of channel sharing.					       │

       Channels are automatically closed when an interpreter is destroyed  and │
       when  the  process  exits.   Channels are switched to blocking mode, to │
       ensure that all output is correctly flushed before the process exits.

       The command returns an empty string, and may generate an	 error	if  an
       error occurs while flushing output.  If a command in a command pipeline
       created with open returns an error, close generates an  error  (similar
       to the exec command.)

       This  illustrates  how  you can use Tcl to ensure that files get closed
       even when errors happen by combining catch, close and return:
	      proc withOpenFile {filename channelVar script} {
		  upvar 1 $channelVar chan
		  set chan [open $filename]
		  catch {
		      uplevel 1 $script
		  } result options
		  close $chan
		  return -options $options $result

       file(n), open(n), socket(n), eof(n), Tcl_StandardChannels(3)

       blocking, channel, close, nonblocking

Tcl				      7.5			      close(n)
                             _         _         _ 
                            | |       | |       | |     
                            | |       | |       | |     
                         __ | | __ __ | | __ __ | | __  
                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 
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